BP (Canada)

KEY POINTS Obesity is a complex chronic disease in which abnormal or excess body fat (adiposity) impairs health, increases the risk of long-term medical complications and reduces lifespan.[1][1] Epidemiologic studies define obesity using the body mass index (BMI; weight/height2), which can stratify

Abstract A conceptual framework for understanding the effects of eustatic control on depositional stratal patterns is presented. Eustatic changes result in a succession of systems tracts that combine to form sequences deposited between eustatic-fall inflection points. Two types of sequences have been recognized: (1) a type 1 sequence, which is bounded at the base by a type 1 unconformity and at the top by either a type 1 or type 2 unconformity and has lowstand deposits at its base, and (2) a type 2 sequence, which is bounded at the base by a type 2 unconformity and at the top by either a type 1 or type 2 unconformity and has no lowstand deposits. Each sequence is composed of three systems tracts; the type 1 sequence is composed of lowstand, transgressive-, and highstand systems tracts, and the type 2 sequence is composed of shelf-margin, transgressive-, and highstand systems tracts. The type 1 sequence is associated with stream rejuvenation and incision at its base, whereas the type 2 sequence is not. Eustacy and subsidence combine to make the space available for sediment to fill. The results of this changing accommodation are the onlapping and offlapping depositional stratal patterns observed on basin margins. Locally, conditions of subsidence and/or uplift and sediment supply may overprint but usually will not mask the effects of global sea level. Any eustatic variation, however, (e.g., irregular eustatic rise or fall, asymmetric fall, slow or rapid rise or fall, and so on) will be globally effective. The significance of eustatic fall-and-rise inflection points is considered with regard to the occurrence of unconformities and condensed sections, respectively. Type 1 unconformities are related to rapid eustatic falls, and type 2 unconformities are related to slow eustatic falls.

Abstract The most common form of incised-valley system develops during a lowering in base level associated with a fall in relative sea level. This form of incised-valley system provides the most complete, and at times, the only evidence of lowstand to early-transgressive deposition in shelf and/or shallow ramp depositional settings. Incised-valley systems of this type are characterized by a flu-vially-eroded, elongate paleotopographic low, generally larger than a single channel, which displays an abrupt basinward shift of facies at its base. The valley fill typically begins to accumulate during base-level rise, and may contain deposits of the following highstand and subsequent sea-level cycles. Two major varieties of incised valley occur during a lowering of sea level: (i) incised-valley systems that have their headwaters in a (mountainous) hinterland and cross a "fall line" (or knickpoint) are here considered to be piedmont incised-valley systems, and (ii) incised-valley systems that are localized within low-gradient coastal plains and that do not cross a "fall line" are here termed coastal-plain incised-valley systems. An incised-valley system that is filled during one depositional sequence is termed a simple fill, whereas a compound fillrecords multiple cycles of incision and deposition. The fill of an incised-valley system that forms in response to a lowering of base level is divisible into three segments: (i) the seaward reaches of the incised valley (SEGMENT 1) is characterized by backstepping (lowstand to transgressive) fluvial and estuarine deposits, overlain by transgressive marine sands and shelf muds; (ii) the middle reach of the incised valley (SEGMENT 2) consists of the drowned-valley estuarine complex that is developed at the time of maximum transgression, overlying a lowstand to transgressive succession of fluvial and estuarine deposits like those in segment 1; and (iii) the innermost reach of the incised valley (SEGMENT 3) lies headward of the transgressive estuarine limit, and extends to the point where changes in relative sea level no longer control fluvial style. Segment 3 is characterized by fluvial deposits throughout its depositional history; however, the fluvial style may change systematically due to changes in base level and the rate of creation of accommodation space. The stratigraphic organization of these incised-valley systems is characterized by a number of stratigraphically-significant surfaces that differ greatly in their origin, geographic extent, and chronostratigraphic significance. Filling of the valley may begin during the lowstand, but typically continues through the succeeding transgression. Thus, the transgressive surface(i.e., the flooding surface separating the Lowstand Systems Tract and the Transgressive Systems Tract) should be present in the lower portion of the fill. It may occur within fluvial deposits or at the fluvial-estuarine contact in segments 1 and 2, and at a correlative change in fluvial depositional style in segment 3. Erosion by tidal currents in tidal inlets or other tidal channels creates a tidal ravinement surfacewhich is confined to the incised valley in segment 1 and the seaward part of segment 2. More regional erosion by waves at the retreating shoreface produces a wave ravinement surfacethat separates fluvial and/or estuarine sediments from overlying marine deposits in segment 1. Both of these surfaces are diachronous, and could become amalgamated with the sequence boundary. In the idealized case, a maximum flooding surfacemay extend throughout the incised-valley fill, passing from its typical position within marine shales in segment 1, through the center of the estuarine deposits in segment 2, into fluvial sediments in segment 3. However, rapid relative sea-level fall after the end of the transgression, or renewed sea-level rise after valley filling (but before the onset of significant progradation), may prevent development of the maximum flooding surface. Compound valley fills may contain multiple sets of these surfaces.

Abstract Modern seismic reflection data may be processed to approximate closely the reflection coefficient series of a sedimentary section. Inversion of the series will produce a low-cut filtered impedance log. Extension of the technique to include density correction and replacement of missing low-frequency components leads to generation of a synthetic sonic log having dimensions and characteristics similar to a conventional borehole sonic log.A synthetic sonic log section provides several advantages over conventional seismic sections, particularly for stratigraphic exploration. Direct depth display largely eliminates the vertical scale distortion inherent in time sections and simplifies integration with other subsurface data. Resolution is generally improved.The process is well adapted to automated generation of stratigraphic sections. Individual rock units are mapped by contours of constant transit-time, to show facies changes and depositional sequences in detail. The detailed measurements of velocity may be used to interpret rock type. Comparison of synthetic sonic log sections to the conventional seismic data from which they were derived, clearly demonstrates improved understanding of subsurface geology.

Summary Positive inversion tectonics involves the reversal of extensional fault movement during contractional tectonics. Basin stratigraphy developed before, during and after extensional fault movements may be described as pre-, syn- and postrift sequences. Growth fault activity may be graphically displayed using thickness changes in stratigraphic intervals from fault footwall to hanging wall. Alternatively, it may be recorded using a hanging wall displacement/distance plot. Contractional reactivation of extensional faults puts progressively older synrift markers into net contraction. The point of change from net extension to net contraction is the null point. Its position in the synrift stratigraphy may be used to quantify the inversion ratio, which is defined as the ratio of contractional to extensional movement. Negative inversion is the reactivation in extension of a significant portion of an existing contractional system. Stratigraphic separation diagrams constructed from geological maps may be used to define the null point of individual faults and to quantify their inversion ratio.

Although many employees are using more information communication technology (ICT) as part of their jobs, few studies have examined the impact of ICT on their well-being, and there is a lack of validated measures designed to assess the ICT factors that may impact employee well-being. Therefore, we developed and validated a measure of ICT demands and supports. Using Exploratory Structural Equation Modeling, we found support for 8 ICT demands (i.e., availability, communication, ICT control, ICT hassles, employee monitoring, learning, response expectations, and workload) and two facets of ICT support (personal assistance and resources/upgrades support). Jointly, the ICT demands were associated with increased strain, stress, and burnout and were still associated with stress and strain after controlling for demographics, job variables, and job demands. The two types of ICT support were associated with lower stress, strain, and burnout. Resources/upgrades support moderated the relationship between learning expectations and most strain outcomes and between ICT hassles and strain. Personal assistance support moderated the relationship between ICT hassles and strain.

Due to its recalcitrance against microbial degradation, biochar is very stable in soil compared to other organic matter additions, making its application to soils a suitable approach for the build-up of soil organic carbon (SOC). The net effects of such biochar addition also depend on its interactions with existing organic matter in soils. A study was established to investigate how the status of pre-existing soil organic matter influences biochar stabilisation in soil in comparison to labile organic additions. Carbon loss was greater in the C-rich sites (C content 58.0 g C/kg) than C-poor soils (C content 21.0–24.0 g C/kg), regardless of the quality of the applied organic resource. Biochar-applied, C-rich soil showed greater C losses, by >0.5 kg/m2.year, than biochar-applied C-poor soil, whereas the difference was only 0.1 kg/m2.year with Tithonia diversifolia green manure. Biochar application reduced the rate of CO2-C loss by 27%, and T. diversifolia increased CO2-C losses by 22% in the C-poor soils. With biochar application, a greater proportion of C (6.8 times) was found in the intra-aggregate fraction per unit C respired than with green manure, indicating a more efficient stabilisation in addition to the chemical recalcitrance of biochar. In SOC-poor soils, biochar application enriched aromatic-C, carboxyl-C, and traces of ketones and esters mainly in unprotected organic matter and within aggregates, as determined by Fourier-transform infrared spectroscopy. In contrast, additions of T. diversifolia biomass enriched conjugated carbonyl-C such as ketones and quinones, as well as CH deformations of aliphatic-C mainly in the intra-aggregate fraction. The data indicate that not only the stability but also the stabilisation of biochar exceeds that of a labile organic matter addition such as green manure.

Abstract Estimates of the quality, Q, factor are commonly obtained from vertical seismic data or stacked surface seismic data. This paper describes a method that allows Q-factor to be estimated directly from common midpoint (CMP) gathers. Absorption of the wavefield is dependent on three parameters: frequency, traveltime in the medium, and medium Q-factor. Assuming that the amplitude spectrum of the seismic source signature may be modeled by that of a Ricker wavelet, we derive an analytical relation between Q-factor and seismic data peak frequency variation both along offset and vertical time direction. The Q-factor is estimated from CMP gathers using a layer-stripping approach.

OBJECTIVE: To assess the prevalence of diagnosed failure-based depression and self-reported symptoms of depression within a sample of elite swimmers competing for positions on Canadian Olympic and World Championship teams. DESIGN: A cross-sectional design. SETTING: Assessments were conducted after the conclusion of the qualifying swimming trials. PARTICIPANTS: The sample consisted of 50 varsity swimmers (28 men and 22 women) based at 2 Canadian universities who were competing to represent Canada internationally. MAIN OUTCOME MEASURES: Diagnosed depression was assessed using a semistructured interview, and symptoms of depression were also assessed by the Beck Depression Inventory II. Performance was measured by changes in swimming time and athlete ranking. RESULTS: Before competition, 68% of athletes met criteria for a major depressive episode. More female athletes experienced depression than their male peers (P = 0.01). After the competition, 34% of athletes met diagnostic criteria and 26% self-reported mild to moderate symptoms of depression. The prevalence of depression doubled among the elite top 25% of athletes assessed. Within this group, performance failure was significantly associated with depression. CONCLUSIONS: The findings suggest that the prevalence of depression among elite athletes is higher than what has been previously reported in the literature. Being ranked among the very elite athletes is related to an increase in susceptibility to depression, particularly in relation to a failed performance. Given these findings, it is important to consider the mental health of athletes and have appropriate support services in place.

The efficacy of the addition of nano-CaCO 3 in accelerating the hydration of ordinary Portland cement (OPC) delayed by the presence of high volumes of supplementary cementitious materials including fly ash and slag was investigated. The conduction calorimetry indicated that the early hydration of OPC was significantly accelerated by the addition of the nano-CaCO 3 and the higher the amount of CaCO 3 addition, the greater was the accelerating effect. The thermogravimetric analysis results showed that the amounts of added CaCO 3 became slightly lower as the hydration took place; however, any new reaction products were not detected by the X-ray diffractometry analysis. The engineering properties, including microhardness and modulus of elasticity, in the early stage of the hydration were remarkably improved by the addition of nano-CaCO 3 . It was suggested that the seeding effect of the nano-CaCO 3 particles and the nucleation of C–S–H caused the enhanced strength development.

Abstract We report classical atomistic molecular dynamics simulations of four structurally diverse model asphaltenes, a model resin, and their respective mixtures in toluene or heptane under ambient conditions. Relatively large systems (∼50 000 atoms) and long time scales (>80 ns) are explored. Wherever possible, comparisons are made to available experimental observations asserting the validity of the models. When the asphaltenes are dissolved in toluene, a continuous distribution of cluster sizes is observed with average aggregation number ranging between 3.6 and 5.6, monomers and dimers being the predominant species. As expected for mixtures in heptane, the asphaltene molecules tend to aggregate to form a segregated phase. There is no evidence of the distinct formation of nanoaggregates, and the distribution of clusters is found to be continuous in character. Analysis of the shape of the clusters of asphaltenes suggests that they are generally spherical in character, with the archipelago models favoring longer prolate structures and the continental model tending toward oblate structures. The aggregates are seen to be diffuse in nature, containing at least 50% solvent on average, being denser in heptane than in toluene. Mixtures of asphaltenes with different architecture are found to have cluster properties that are intermediate between those of the individual components. The presence of resins in the mixture does not appear to alter the shape of the asphaltene aggregates or their size or density when toluene is the solvent; on the other hand, the resins lead to an increase in the density of the resulting aggregates in heptane. Quantification of these observations is made from histograms of the cluster distributions, potential of mean force calculations, and an analysis of the shape factors. We illustrate how the time scales for complete aggregation of molecules in heptane are longer than the longest of the simulations reported in the open literature and as an example report a long simulation (0.5 μs) that fails to reach an equilibrium state, suggesting that acceleration techniques (e.g., using coarse-grained models) are needed to appropriately explore these phenomena.

ABSTRACT There were 5513 wells drilled in western Canada during 1989, 30% fewer than in 1988. Total meterage drilled was 6,459,797 m, for an average well depth of 1172 m. Exploratory drilling in 1989 dropped by 13% and development drilling by 40% from 1988 levels. British Columbia was the only area in western Canada with increased activity. The industry continued to acquire more acreage for less total bonus at provincial Crown sales throughout western Canada. During 1989, 3,564,827 ha were acquired for a total bonus of $484,872,0005. Although the total disposition of Crown lands decreased only 4%, the average bonus dropped to $136/ha, down 26% from 1988. In Alberta, the most active exploration areas were the southern and eastern Mesozoic gas play, the western deep Devonian gas play, the oil plays on and adjacent to the Peace River arch, and the Middle Devonian carbonate oil plays in the northwest. In British Columbia, the most active exploration areas were the Mesozoic and Paleozoic gas plays in the northeastern portion of the province. For the first time in 5 years, Crown drilling rights were issued within the Fraser Valley in the southwest. There was a focus on gas exploration in the province as pipeline reversal was implemented, permitting access to Canadian and California markets through the Alberta transportation network. In Manitoba, exploration and development activity continued to decline. In northern Canada, exploratory drilling success, offering of Crown lands for exploration, approval of gas exports, and indications that many of the Native lands claims may be approaching settlement, all provided exploration encouragement for the next decade. Exploration activities occurred throughout the Northwest Territories from the offshore Beaufort to the southern border. In Saskatchewan, active exploration areas were shallow Mesozoic gas plays in the western portions of the province and deep Paleozoic oil plays in the south.

ABSTRACT Using clusters of locations obtained from Global Positioning System (GPS) telemetry collars to identify predation events may allow more efficient estimation of behavioral predation parameters for the study and management of large carnivore predator‐prey systems. Applications of field‐ and model‐based GPS telemetry cluster techniques, however, have met with mixed success. To further evaluate and refine these techniques for cougars ( Puma concolor ), we used data from visits to 1,735 GPS telemetry clusters, 637 of which were locations where cougars killed prey >8 kg in a multi‐prey system in west‐central Alberta. We tested 1) whether clusters were reliably created at kill locations, 2) the ability of logistic regression models to identify kill occurrence (prey >8 kg) and multinomial regression models to identify the prey species at a kill cluster, and 3) the duration of monitoring required to accurately estimate kill rate and prey composition. We found that GPS collars programmed to attempt location fixes every 3 hours consistently identified locations where prey >8 kg were handled, and cluster creation was robust to GPS location acquisition failures (poor collar fix success). The logistic regression model was capable of estimating cougar kill rate with a mean 5‐fold cross validation error of <10%, provided the appropriate probability cutoff distinguishing kill clusters from non‐kill clusters was selected. Logistic models also can be used to direct visits to clusters, reducing field efforts by as much as 25%, while still locating >95% of all kills. The multinomial model overpredicted occurrence of primary prey (deer) in the diet and underpredicted consumption of alternate prey (e.g., elk and moose) by as much as 100%. We conclude that a purely model‐based approach should be used cautiously and that field visitation is required to obtain reliable information on species, sex, age, or condition of prey. Ultimately, we recommend a combined approach that involves using models to direct field visitation when estimating behavioral predation parameters. Regardless of the monitoring approach, long continuous monitoring periods (i.e., >100 days of a 180‐day period) were necessary to reduce bias and imprecision in kill rate and prey composition estimates.

BACKGROUND: Previous research has established that general sleep screening questionnaires are not valid and reliable in an athlete population. The Athlete Sleep Screening Questionnaire (ASSQ) was developed to address this need. While the initial validation of the ASSQ has been established, the clinical validity of the ASSQ has yet to be determined. The main objective of the current study was to evaluate the clinical validity of the ASSQ. METHODS: Canadian National Team athletes (N = 199; mean age 24.0 ± 4.2 years, 62% females; from 23 sports) completed the ASSQ. A subset of athletes (N = 46) were randomized to the clinical validation sub-study which required subjects to complete an ASSQ at times 2 and 3 and to have a clinical sleep interview by a sleep medicine physician (SMP) who rated each subjects' category of clinical sleep problem and provided recommendations to improve sleep. To assess clinical validity, the SMP category of clinical sleep problem was compared to the ASSQ. RESULTS: The internal consistency (Cronbach's alpha = 0.74) and test-retest reliability (r = 0.86) of the ASSQ were acceptable. The ASSQ demonstrated good agreement with the SMP (Cohen's kappa = 0.84) which yielded a diagnostic sensitivity of 81%, specificity of 93%, positive predictive value of 87%, and negative predictive value of 90%. There were 25.1% of athletes identified to have clinically relevant sleep disturbances that required further clinical sleep assessment. Sleep improved from time 1 at baseline to after the recommendations at time 3. CONCLUSIONS: Sleep screening athletes with the ASSQ provides a method of accurately determining which athletes would benefit from preventative measures and which athletes suffer from clinically significant sleep problems. The process of sleep screening athletes and providing recommendations improves sleep and offers a clinical intervention output that is simple and efficient for teams and athletes to implement.

Abstract Seven hundred seventy liters of a dense nonaqueous phase liquid (DNAPL), tetrachloroethylene (PCE), were released into an isolated volume of a completely saturated natural sandy aquifer. The release was monitored over a period of 984 hours with a variety of geophysical methods including ground penetrating radar, time domain reflectometry, in situ resistivity, and a neutron soil moisture probe. The PCE formed a pool on a low permeability layer at approximately 1 m depth and spread over an area exceeding 32 m 2 . In its course of downward migration, the PCE subsequently formed eight smaller pools. At the end of the experiment an estimated 41 percent of the total PCE volume remained trapped in the upper pool. The PCE mass and its spatial moments were calculated from radar reflection amplitudes. Between 48 and 100 percent of the PCE mass was accounted for by radar measurements. The center of mass moved a total of 0.5 m south southeast and 1.3 m downward. Spatial variances showed that the greatest lateral spreading occurred in the east‐west direction. The results demonstrate that natural heterogeneities, even in a relatively homogeneous aquifer, can cause DNAPLs to spread laterally over large areas in the subsurface. This experiment also demonstrated that while the ability of geophysics to uniquely measure the presence of DNAPL is limited, certain techniques are well‐suited to monitoring changes in DNAPL saturation.

The first images of Jupiter, Io, Europa, and Ganymede from the Galileo spacecraft reveal new information about Jupiter's Great Red Spot (GRS) and the surfaces of the Galilean satellites. Features similar to clusters of thunderstorms were found in the GRS. Nearby wave structures suggest that the GRS may be a shallow atmospheric feature. Changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on Io. Patchy emissions were seen while Io was in eclipse by Jupiter. The outer margins of prominent linear markings (triple bands) on Europa are diffuse, suggesting that material has been vented from fractures. Numerous small circular craters indicate localized areas of relatively old surface. Pervasive brittle deformation of an ice layer appears to have formed grooves on Ganymede. Dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution.

BACKGROUND: There is a growing concern for microbial resistance as a result of overuse of antibiotics. Although guidelines have focused on the use of antibiotics for surgery in general, few have addressed plastic surgery specifically. The objective of this expert consensus conference was to evaluate the evidence for efficacy and safety of antibiotic prophylaxis in plastic surgical procedures. METHODS: THE AUTHORS: searched for existing high-quality systematic reviews for antibiotic prophylaxis in the literature from the MEDLINE, Cochrane Library, and Embase databases. All synonyms for antibiotics were combined with terms for relevant plastic surgery procedures. The searches were not limited by language, and included all study designs. In addition, supplemental hand searches were performed of bibliographies of relevant articles, and extensive "related articles." Meta-analyses were performed and reviewed by experts selected by the American Association of Plastic Surgeons to reach consensus recommendations. RESULTS: Database searches identified 4300 articles, from which 2042 full-text articles were identified for eligibility. De novo meta-analyses were performed for each plastic surgical category. In total, 67 studies met the inclusion criteria, including nine for breast surgery, 17 for head and neck surgery, 10 for orthognathic surgery, seven for rhinoplasty/septoplasty, 19 for hand surgery, five for skin surgery, and two for abdominoplasty. CONCLUSIONS: Systemic antibiotic prophylaxis is recommended for clean breast surgery and for contaminated surgery of the hand or the head and neck. It is not recommended to reduce infection in clean surgical cases of the hand, skin, head and neck, or abdominoplasty.

Abstract An Industry Consortium (BP, ChevronTexaco and Nalco Company) conducted a joint research project known as Bright Water. The goal of this project was to develop a novel, time-delayed, highly expandable particulate material that would improve the sweep efficiency of a water flood. In November 2001, the first of these water flood profile modification treatments was pumped in the Minas field, as reported in SPE 84897 (1). An overview of the development of the particulate system is given in the present paper. The polymeric "kernel" particles are capable of "popping" under the influence of temperature and time. The expanded particle can then provide resistance to fluid flow in porous media. Various properties of the kernel dispersions are summarized. Laboratory tests representative of the deployment of the product are presented to illustrate the injection, propagation and popping of the particles. Screening criteria for application of the product are reviewed and related to product selection for the field trial.

An experiment was conducted to compare the rates of disappearance of amino acids (AA) from the small intestine and their net appearance in the blood draining only the small intestine (mesenteric-drained viscera) and the whole gastrointestinal tract (portal-drained viscera) of cows fed a silage-based diet supplemented or not with ruminally protected Met. Five lactating dairy cows (118+/-4 DIM) equipped with duodenal and ileal cannulae (n = 2) or a duodenal cannula only (n = 3), two of which were multicatheterized, were fed a TMR top dressed with 0 or 72 g of ruminally protected Met per day. The addition of ruminally protected Met to the diet increased the duodenal flux of Met leading to a higher apparent digestibility of Met in the small intestine. Sixty-six percent of Met from ruminally protected Met bypassed the rumen and 82% of that Met disappeared from the small intestine. Arterial plasma Met concentrations numerically increased with ruminally protected Met (45 vs. 18 microM), while total AA concentration decreased. Feeding ruminally protected Met resulted in higher concentrations of urea-N and glucose in arterial plasma. Milk production and milk composition were unaffected. The disappearance of essential AA across the small intestine was equivalent (101%) to their flux through the mesenteric-drained viscera while the portal:mesenteric-drained viscera flux ratio for each essential AA varied from 38% for Thr to 76% for Phe. The portal:mesenteric-drained viscera flux ratio for Met was 66%. These results confirm observations made with pigs and sheep.

ABSTRACT The structural index (SI) is based on the concept of Euler homogeneity, a description of scaling behavior. It has found wide use in potential-field depth estimation and is a constant integer for simple sources with single singularities (points, lines, thin-bed faults, sheet edges, infinite contacts). For these cases, the SI is identical to the index of a simple power-law field fall-off with distance. The simple Euler formulation is only strictly correct for such simple sources and integer SI values. The widespread use of the simple Euler method on more complex structures, using fractional SI values is likely to produce misleading results because the SI is no longer a constant for any given source. We examine a recently published example that used an arbitrary SI to estimate depth to the base of the crust for Africa and produced misleading results. Extension to more complex sources such as tabular bodies or thick steps requires one of several more generalized approaches, which recognize all variables with spatial dimensions (including source size parameters) and may make use of negative SI values, address omitted variable bias or use an explicit multiple-source formulation. An alternative approach using homogeneity via differential similarity transforms is probably the best way forward. An error in the literature is corrected: the gravity SI for a finite step is −1, but it requires a more generalized formulation. We develop a new terminology, fractional SI, s, which is permitted to take fractional values and makes no pretense to honor concepts of homogeneity.